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Aspirin is not recommended for the prevention of travelers’ thrombosis

Most travelers have experienced jet lag. The common symptoms—insomnia, fatigue, change in appetite, irritability—are due in part to your body’s cyclical hormone production being temporarily out of synch with your activities. After several days at your destination, your body’s biological clock (circadian rhythm) becomes reset, and the symptoms subside. In general, it takes the body 1 day to adjust for each time zone crossed.

Like many disorders that have no cure, there are lots of proposed jet lag remedies and preventatives. Numerous travelers have tried jet lag “diets.” More recently, exposures to artificial light sources and melatonin have been touted as being effective in resetting the body’s clock. Note: For short stays of 3 days or less, adjustment of the body clock is not possible and should not be attempted.

Jet Lag Diets

Food has no effect on jet lag. There has never been any scientific evidence that jet lag diets do any good, and they have declined in popularity. Many travelers find these diets too complex and tedious to follow. Any claimed benefits most likely are psychological, due to a placebo effect.

Jet Lag Formulas

These vitamin-amino acid formulas or homeopathic preparations supposedly help reset your biorhythms, but like jet lags diets, they are not scientifically proved and work primarily by placebo effect. Some jet lag formulas previously contained the amino acid l-tryptophan, which has proved mild sedative qualities, but the purified substance is now banned. The amino acids and vitamins in jet lag preparations are the same as those available in any drugstore.

Light Exposure

Light exposure seems to play a role in resetting circadian rhythms. The mechanism involves suppression of the hormone melatonin, which is secreted by the brain’s pineal gland. The current dogma is that for eastward travel additional morning sunlight (whether cloudy or not) is beneficial, whereas for westward travel, afternoon light is important. Special high-intensity lights (>10,000 lux) are available to help accomplish this end. Regardless of travel destination and arrival time, recent studies suggest that exposure to outdoor light at any time of day assists in readjustment of your circadian rhythm.

Melatonin

Ten years of placebo-controlled studies have shown that the hormone melatonin can reset your body’s internal clock. In one study, travelers were given 3 to 5 mg of melatonin at the “destination nighttime” for 3 days before travel, then for 3 days after arrival. They experienced much less fatigue, required less time to normalize their sleep patterns, and scored better on a visual analog scale. Some other studies, however, have shown no significant beneficial effect in about 25% of recipients, and up to 10% of travelers taking melatonin have adverse side effects (e.g., headache and excessive drowsiness). In summary, melatonin appears to be somewhat beneficial, but there is much individual variation in response to this hormone. Although there is little evidence of toxicity, concerns have been raised about melatonin’s safety because the drug’s strength, quality, and purity are not standardized. Also, there are little data on optimal dosing and timing of administration.

Researchers point out that little is known about melatonin’s long-term safety, its effects on reproduction, and its possible dangers to people with autoimmune diseases. Because melatonin is a hormone, it is not recommended for children or during pregnancy. It should also be noted that unidentified chemical impurities have been detected in some melatonin preparations.

The Response in the Brain to Light Signals The response to light signals in the brain is an important key factor in sleep:

Light signals travel to a tiny cluster of nerves in the hypothalamus in the center of the brain, the body’s master clock, which is called the supra chiasmatic nucleus or SCN.

This nerve cluster takes its name from its location, which is just above ( supra) the optic chiasm. The optic chiasm is a major junction for nerves transmitting information about light from the eyes.

The approach of dusk each day prompts the SCN to signal the nearby pineal gland (named so because it resembles a pine-cone) to produce the hormone melatonin.

Melatonin is thought to act as the body’s time-setting hormone. The longer a person is in darkness the longer the duration of melatonin secretion. Secretion can be diminished by staying in bright light. Melatonin also appears to serve as a trigger for the need to sleep, hence the use of melatonin in the treatment of jet lag.

Sleeping Pills

Insomnia is one of the most troublesome symptoms of jet lag. While you’re trying to fall asleep, your internal clock is saying “wake up.” If you need to adapt more rapidly to the new time zone, and you have a problem with insomnia, ask your doctor to prescribe a sleeping pill. The first of the nonbarbiturate, short-acting sleeping pills was Halcion (triazolam), a benzodiazepine (similar to Valium). Although safe and rapidly effective, there were reports (albeit extremely rare) of next-day memory impairment or amnesia associated with this drug, especially after long-haul flights with the consumption of alcohol en-route. Also, the dose of Halcion was in the higher range (0.5 mg) in these patients.

Most sleeping pills fall into two categories:

Benzodiazepines These are often called tranquilizers and include diazepam (Valium), alprazolam (Xanax), and lorazepam (Ativan). They are commonly used to treat anxiety. Shorter-acting benzodiazepines such as temazepam (Restoril), triazolam (Halcion), estazolam (ProSom), and lorazepam (Ativan) are most often prescribed to treat insomnia. The longer-acting benzodiazepines Valium and Xanax are sometimes prescribed for insomnia, but they stay in the blood longer and are more likely to cause impairment or “hangover” the next day—perhaps when you are arriving at your destination!

Note: Flurazepam (a sleeping pill marketed under the brand names Dalmane) has the longest half-life of all of the benzodiazepines (40-250 hours), and may stay in the bloodstream for up to four days. Flurazepam is therefore unsuitable as a sleeping medication for some individuals due to next day sedation.

One advantage of benzodiazepines is that they nearly all are available in inexpensive generic forms costing <1 dollar per pill versus >3 dollars for the newer branded drugs.

Nonbenzodiazepines For travelers who want an alternative to the benzodiazepine hypnotics newer agents are now available; they include the following:

Ambien (zolpidem – now a generic): Dose: 5 to 10 mg

Ambien-CR (not available as a generic)

Sonata (zaleplon): Dose: 10 to 20 mg

Lunesta (eszopiclone): Dose: 1 to 3 mg

Rozerem (ramelteon): Dose: 8 mg (Stimulates release of melatonin)

These drugs are chemically unrelated to the benzodiazepines. They have rapid onset, adequate duration of action, and claim minimum or no residual effect on daytime performance. Bear in mind, however, that drug effects vary from one person to another and under different circumstances. Transient memory impairment has been reported with nonbenzodiazepine drugs (albeit with a low incidence) and there are reports of Ambien-induced sleepwalking and late-night binge eating. Taking any of these pills with alcohol or other medications can intensify side effects, sometimes unpredictably.

Each drug has its advantages and disadvantages. Only take Lunesta or Ambien if you have at least 8 hours for sleeping, e.g., on a long-haul flight across the Pacific. Sonata wears off after 4 hours and would be appropriate for a shorter flight, e.g., an overnight from New York to London. A short-acting benzodiazepine (above) works in this scenario, too.

Are sleeping pills safe? Generally yes, but all sleeping pills share some drawbacks. You may develop tolerance, so the pills become less effective; and if you do use them every night, you may become dependent. If you suddenly stop taking the drug, you’ll get rebound insomnia for several nights. There is an increase in the numbers of falls and fractures in the elderly who take sleeping pills.

Use the pills until jet lag wears off—usually about a week—and take them in the lowest effective dose. (Only Lunesta and Rozerem are FDA-approved for long-term use.) According to the Harvard Medical School Health Letter, “Taking sleeping pills for a short period—perhaps a few days—can be quite helpful . . . and there is little controversy about prescribing them to help people through a crisis.”

So, What to Do?

Before taking medication or using techniques to prevent jet lag, consider the following:

Is the treatment safe? Are there side effects?

Is the treatment effective?

Is the treatment practical and cost effective?

What Really Causes Jet Lag Anyway?

Feeling tired and irritable after a long trip is not due entirely to changes in your circadian rhythms. The issue is more complex. Consider the typical scenario:

For several days before departure, you are frantically taking care of what seems like a thousand and one last minute errands and details.

You are probably too keyed up to get enough sleep.

Your normal eating and drinking patterns are disrupted.

You are somewhat apprehensive about flying.

You are anxious about leaving home and/or your family.

You fight heavy traffic getting to the airport.

You park your car, but wonder if it will be safe.

You carry a heavy suitcase a half a mile to the check-in point and hope it won’t get lost.

You catch a connecting flight and you stand in line again at check-in.

You clear security checkpoints.

Then you wait in a crowded airport lounge because your overseas flight is delayed by hours.

It’s no surprise that you’re feeling stressed out even before takeoff. Add to this a lack of sleep en route, cramped seating, further dehydration, and even constipation. Then, after arrival in a foreign country, you face still more hassles simply getting to your hotel. No wonder you’ve got jet lag.

The Health Guide takes the following view: Jet lag is not a single entity and the symptom complex will probably never be completely alleviated by a single treatment. The symptoms you experience are usually a combination of travel-related physical and emotional stresses, sleep deprivation, plus the biological effect of your circadian rhythm being out of synch.

En-Route Strategies to Reduce Jet Lag

Don’t drink too much alcohol—If you are a drinker, there’s no reason not to have your cocktail, but remember that although alcohol is a depressant drug, it may cause rebound nervous stimulation, interfering with sleep.

Don’t drink too much coffee—Excess caffeine may cause nervousness and possibly insomnia. Excess caffeine stimulates gastric acid production, which can cause heartburn. However, if you habitually drink many cups of coffee each day, missing your “caffeine fix” during your flight may not be a good idea. You might get symptoms of caffeine withdrawal and feel even worse (e.g., headache)! Coffee-drinker strategy: Reset your watch to the destination time when you board the aircraft. Drink your coffee en-route at the destination time that corresponds to your regular “caffeine fix” time at home.

Drink water and fruit juices—They are good substitutes for (or complements to) alcoholic drinks and coffee. You may be somewhat dehydrated at the beginning of the flight due to disrupted eating and drinking habits before departure, and your sense of thirst may also be increased by breathing low-humidity cabin air.

Sleep en-route?—This may be hard to avoid, especially if your flight is to Australia or Asia from North America. No studies have been done to assess whether sleeping en-route significantly alters the symptoms of jet lag. You’ll probably feel better on arrival, but falling asleep later might be more difficult.

After Arrival at Your Destination

The most important principle is to begin all activities, including eating and sleeping, at destination times as soon as possible. If you have an evening arrival, have a light dinner and go to bed late. The next day try to eat and sleep according to the local time.

If you have a morning arrival, stay active during the day and get as much exposure to natural light as possible, if your schedule and the weather permit. If possible, don’t nap, but overpowering fatigue should not be resisted. If you do nap, keep it to under 45 minutes to avoid Stage IV (REM) sleep, which causes grogginess on awakening. Note: For trips less than 3 days, short naps should be taken when you feel most tired.

Take a sleeping pill if you have troubling insomnia. Discontinue sleeping medication after 3 to 5 nights.

The Myth of Dehydration

For many years it has been touted by the travel media that dry cabin air in jet airliners causes dehydration, which presumably could aggravate jet lag. The recommended remedy is usually to drink extra fluids en route, sometimes as much as a glass of water every hour. However, the Medical Director of British Airways Aviation Medical Services has found (as reported in the medical journal Lancet) that low cabin humidity causes, at most, only a 3-ounce water loss during an 8-hour trip. The reason you think you are dehydrated is because your mouth is dry from breathing dry air, not because you actually are dehydrated. In fact, the stress of travel causes your body to retain water.

Also advised: “Avoid caffeine and alcohol, these will also dehydrate you.” This advice is not true. According to a study from the University of Nebraska Medical Center, healthy adults showed the same “hydration status” (as determined from urine analyses and other tests) when they drank caffeinated beverages, such as coffee or caffeinated colas as when they drank only water and/or fruit drinks. There is no net loss of water from drinking coffee. Concentrated alcoholic drinks, in excess, may cause a mild diuresis, but beer, wine, and many mixed drinks contain lots of water and won’t cause dehydration. Therefore, dehydration from dry cabin air, aggravated by certain beverages, appears to be a myth, and compulsively drinking extra water en route is both inconvenient and unnecessary.

Keep the Problem of Jet Lag in Perspective

Enjoying your vacation is more important than fighting jet lag. Don’t waste your time following complex jet lag diets and cures that have not been shown to work. Try not to worry too much about jet lag. Less than one half of travelers report significant symptoms.

Business Travelers If you are traveling on important business, you probably have more need than others to reduce the symptoms of jet lag. Consider the following strategies: (1) fly first- or business-class to improve the chances of sleeping en route; consider taking a short-acting sleeping pill (2) budget, if possible, 1 or 2 extra days after arrival to rest and recuperate before business activities; or (3) break up a long trip (>6 time zones) along the way for 1 or 2 days.

Motion Sickness

Strictly speaking, motion sickness is neither an illness nor a “sickness” but a normal, albeit exaggerated, response to unfamiliar motion of increased intensity and duration. Nausea, sweating, salivation, and vomiting are the usual symptoms. If vomiting does occur, it is frequently followed by drowsiness and lethargy.

Motion sickness occurs most commonly with acceleration in a direction perpendicular to the longitudinal axis of the body, which is why head movements away from the direction of motion are so provocative. Vertical oscillatory motion (appropriately called heave) at a frequency of 0.2 Hertz is most likely to cause motion sickness. (This frequency would be experienced on board a ship with a roll rate of 5 seconds.) The incidence of motion sickness falls quite rapidly at higher frequencies. The apparent protection at these higher frequencies helps explain why motion sickness is commonly experienced on camelback, but not on horseback, and on board ships, but not while windsurfing.

Risk Factors

Sea > Air > Car > Train

Women > Men

Inexperienced travelers > Experienced travelers

Young age > Older age

Passengers > Crew

Passengers > Driver

Motion sickness occurs in about 1% of airline passengers. Symptoms are rare in children younger than age 2 and peak between the ages of 3 and 12. The elderly are less susceptible.

Preventing/Treating Motion Sickness

Don’t travel on an empty stomach; this seems to promote symptoms. If you feel yourself becoming nauseated, keep your head stationary. Don’t read, but do listen to music if you have a portable radio, iPod, or airline headset. A stable head position is very important in controlling motion sickness because your inner ears contain the balance “gyroscopes” that monitor and coordinate motion and body position.

Increasing ventilation, decreasing food intake, and avoiding alcohol are other techniques to reduce motion sickness. For those interested in natural remedies, ginger root may offer some benefit.

Body Position On a boat, try to stay amidships. Lie supine with your head supported on pillows. Keep your head still and your eyes closed. If on deck, look out at the horizon. One trick: pretend you are “dancing with the ship.” On airliners, either (1) press your head against the seat in front of you, or (2) lean back in the seat, keep your head still, and look straight ahead. In cars, sit in the front seat. Look forward at the horizon, rather than out the side windows.

Acupressure bands (Sea-Bands)—Some people swear by these wrist bands with the plastic beads, but a study conducted by Condé Nast Traveler magazine (October 1991) found no measurable effect on the symptoms of seasickness.

Drugs

Stimulation of nerve fibers in the balance center of the inner ear (the labyrinth) causes the symptoms of motion sickness. The drugs used to control motion sickness not only reduce the activity of these nerve fibers but also appear to act directly on the body’s vomiting center located in the brainstem. The drugs commonly used to prevent motion sickness are the scopolamine preparations and the antihistamines.

Scopolamine

Scopolamine is a drug extract (alkaloid) of the nightshade plant. It is similar to another extract, popularly called belladonna, and known in medicine as atropine. The most frequent side effect of these drugs is dryness of the mouth, but blurred vision, drowsiness, and urinary retention can also occur.

TRANSDERM SCŌP The Transderm Scōp System (Fig. 4.1) is a circular flat patch that delivers 1.0 mg of scopolamine at a constant rate over 3 days. Because of its prolonged action, it is especially useful for seasickness. Travelers may want to try it for a few days before departure to identify any adverse effects.

SCŌPACE (scopolamine hydrobromide) This drug is an oral form of scopolamine with a duration of 6 to 8 hours. It acts more rapidly than the scopolamine patch. The more rapid onset and shorter action make it better suited for airline or automobile travel. The dosage range is 0.4 to 0.8 mg. You should take it on an empty stomach 1 hour before departure. The dosage can be titrated for best effect. Tablets are available through a compounding pharmacy. The drug is also available as a patch.

Ginger This natural motion sickness remedy is safe and moderately effective and is readily available in health food stores.

The small patch placed behind the ear releases minute amounts of scopolamine that permeate the intact skin at a preprogrammed rate over a 72-hour period. The scopolamine is directly absorbed into the blood stream. Scopolamine acts on the nerve fibers of the inner ear and brainstem to reduce nausea and vomiting. The transdermal patch should not be used by children, travelers with glaucoma, or men with prostrate enlargement. Confusion in the elderly may occur.

Antihistamines

Although scopolamine is considered to be the more effective drug for the treatment of motion sickness, many physicians prefer antihistamines because they produce fewer adverse effects (e.g., dry mouth, blurred vision) than scopolamine. Drowsiness is the most common antihistamine side effect, which can be troublesome if you need to drive a car. Drowsiness, on the other hand, can help you sit or lie quietly and thus may be beneficial on a boat or a plane.

Antivert (meclizine) The initial adult dose is 25 to 50 mg. Take 1 hour before departure. Repeat every 12 to 24 hours, as needed, for the duration of the journey. Available by prescription only.

Dramamine (dimenhydrinate) Available without prescription. This drug has a rapid onset of action, and you can use it for either prevention or treatment of symptoms. Adults and children older than 12 years should take one or two tablets every 4 to 6 hours, as needed. Start 1 hour before embarkation. Follow package instructions for younger children.

Phenergan (promethazine) The average adult dose is 25 mg taken twice daily. Take the first dose 30 minutes to 1 hour before embarkation and repeat in 8 to 12 hours, as necessary. Suppositories are quite helpful. For children: Phenergan tablets, syrup, or rectal suppositories, 12.5 to 25 mg (for larger children), twice daily may be administered. This drug, available by prescription, may be the most effective of the antihistamines for the treatment of motion sickness. Contraindicated for children under age 2.

Which One to Choose? Given the choice of motion sickness medications, how is one to choose? A recent comparative trial of seven commonly used agents to prevent motion sickness showed that they all performed equally well.

Sinuses and Ears

When traveling by commercial airliner, you will be cruising at an altitude of 30,000 to 45,000 feet above sea level. Your cabin will be pressurized to an altitude of 6,000 to 8,000 feet above sea level. The air contained in your middle ear and sinuses will expand by about 25% and will usually escape without causing any symptoms. During descent, however, cabin air pressure starts to increase and exceeds the pressure in the middle ear. To allow equalization of pressure on either side of the eardrum, the eustachian tube must open to allow air to enter from the back of your nose. If necessary, clearing the tube can usually be accomplished by yawning or swallowing. Pinching your nostrils and slowly forcing air into the ears can assist this process. Chewing gum can also help contract the muscles at the end of the tube to allow passage of air up into the middle ear.

If the pressure difference between your middle ear and the nasopharynx (back of the throat) becomes too great during descent, the end of the eustachian tube might collapse completely, making further ventilation of the middle ear impossible (Fig. 4.2). If this occurs, pressure will continue to rise outside the eardrum (tympanic membrane), causing painful stretching and inward bulging of this structure. You might experience dizziness, vertigo, and decreased hearing. There could be bleeding into the middle ear from ruptured blood vessels. More commonly, you might experience several hours, rarely days, of pain and pressure in the ear. During this period of inadequate middle ear ventilation, an acute middle ear infection requiring antibiotics might develop.

Descent from cruising altitude increases pressure on the cnal side of the drum (A), which must be equalized in the middle ear (B). This can be effected only by airflow via the nasophargnx through the Eustachian tube (C). If the later is not open, airflow is impeded (D), and the relative negative pressure in the middle ear sets in motion a chain of damaging effects – beginning with pain due to the stretching of the tympanic membrane.

If your sinus openings are blocked, pressure symptoms will develop over that particular sinus where air is trying to enter. You may feel a headache over the lower forehead or eyebrows, or over your cheek and around your eyes.

Prevention and Treatment Your ear structure may be such that you may have difficulty adapting to the pressure changes described. (You would probably also note similar symptoms when scuba diving, traveling in high-speed elevators, or even driving in the mountains.) In this case, you may benefit from a decongestant. A recent study concluded that taking the oral decongestant (pseudoephedrine—Sudafed) decreases the incidence of ear pain and discomfort associated with air travel, but that using a popular decongestant nasal spray (oxymetazoline—Afrin) is only minimally effective. The Health Guide, however, sees no reason why these drugs shouldn’t be taken together. Note: There are reports of pseudoephedrine (which is similar to the recently banned stimulant, ephedrine) triggering heart attacks and stroke even in otherwise healthy young people. Be sure not to exceed the recommended dose.

EarPlanes These devices regulate the air flowing into and out of the ear thereby alleviating ear pain caused by rapid changes in cabin pressure. Inside, porous ceramic elements slow down rapid pressure changes, giving the eustachian tubes more time to equalize pressure between your middle ear and the cabin.

EarPlanes are recommended for travelers who must fly with colds, allergies, or sinus infections. Available online.

If you are suffering from an acute ear infection, sinusitis, or an upper respiratory infection, you might have too much swelling and edema of the nasal mucous membranes to allow equalization of pressure during air travel. You probably should not fly under these conditions. If in doubt, consult your physician or an ear-nose-throat specialist.

Here is a summary of the steps you can take to reduce ear and sinus discomfort when traveling by air:

If you are suffering from hay fever (allergic rhinitis), have your doctor prescribe a nasal steroid spray such as Vancenase or Beconase plus the nonsedating antihistamine Zyrtec. In addition, take an oral decongestant such as pseudoephedrine (Sudafed). Start treatment several days before departure.

If your problem is simple congestion from a head cold, or if you have a history of trouble equalizing middle-ear pressure, start decongestants. Use an oral decongestant, plus a nasal spray, such as oxymetazoline (Afrin) or phenylephrine (Neosynephrine). Start Sudafed at least one day before departure. Use the nasal spray 1 to 2 hours before landing.

Have your doctor prescribe an antibiotic if you have signs of a serious sinus infection (facial pain, fever, thick nasal discharge, or postnasal drip). Most cases of sinusitis, however, are caused by viruses and don’t respond to antibiotics.

Blow your nose frequently to remove mucus.

Remain awake during descent to keep up with pressure changes. Pinch your nose and blow air up into the eustachian tube, as necessary.

Infants: During descent, they should be in a sitting position only when given their bottles, which should contain only water.

Cabin Air

Contrary to popular belief, the cabin air in airliners is not a major source of contamination. Although cabin air contains varying amounts of carbon dioxide, ozone, volatile organic compounds, dust particles, and microbial aerosols, the risk of contamination (especially the risk of acquiring an infectious disease) is practically eliminated by the filtering and air exchange mechanisms used in today’s airliners. According to Thomas Bettes, M.D., M.P.H., former regional medical director for American Airlines, there are fewer microbial aerosols in an airliner than in any other public location. In fact, the heating and filtration to which cabin air is subjected maintain their qualities to those of an operating room with the exception of increased carbon dioxide.

The risk of airborne illness is not related to inadequate filtration of cabin air but rather to being in close contact with a passenger who happens to have a communicable disease (such as tuberculosis or the flu) that can be transmitted directly to you when that person coughs in your direction and you happen to inhale the infected droplets.

Traveler’s Thrombosis

Sitting and traveling for long periods put you at a slight risk for developing a blood clot in your leg. Called deep vein thrombosis (DVT), the clot can break off and move to the lungs, possibly causing a fatal pulmonary embolism. But how many travelers get a DVT in the first place? Estimates of the incidence of traveler’s thrombosis vary dramatically, from a handful of cases to perhaps tens of thousands annually.

One problem is defining the condition. The vast majority of blood clots dissolve on their own, and the passenger is never the wiser. Problems (like a swollen leg) sometimes don’t arise for days after the flight, and the traveler doesn’t realize the two events are related. A study published in the medical journal Lancet, where the authors used ultrasound as the screening method, found that as many as 10% of the subjects studied developed asymptomatic deep vein thrombosis in the calf during flights of 8 hours or longer. But other investigators have found a lower incidence. The LONFLIT study series, for example, found an incidence of only 4% to 5% using ultrasound screenings, and that was among high-risk subjects.

Another report (Lancet, October 2000) downplays the risk. Of 788 patients with DVT that were studied and compared with a control group, there was no association of travel (by air, bus, automobile, train, or boat) with DVT. These authors concluded that “these results do not lend support to the widely accepted assumption that long traveling time is a risk factor for venous thrombosis. Even for journeys lasting more than 5 hours no association was apparent.”

What about pulmonary embolism, the complication of DVT that threatens lives? A study in 2001, found just 56 cases of confirmed pulmonary embolism among the 135 million passengers who arrived at Charles de Gaulle airport. The authors also discovered that the risk of pulmonary embolism does increase with the distance traveled. For those flying 3,000 miles, the risk was 1.5 cases per million. At 6,000 miles, the risk grew to 4.8 cases per million.

Basing their opinion on these and other studies, the World Health Organization has concluded that there is a definite link between long-distance air travel and deep vein thrombosis, but they say it is small, and mostly affects people who are already at risk for blood clots.

Symptoms and Diagnosis

Pain and swelling of a leg are typically noted, but some DVTs are silent, or cause swelling without any pain. If a DVT results in a pulmonary embolus (PE), shortness of breath and/or chest pain usually occur, but sometimes fainting is the first symptom. A blood test called D-dimer assay (which measures blood clot fragments) can be used to screen for DVT, but if there is a high suspicion of DVT or a PE based on symptoms, an ultrasound examination of the leg, or a computed tomogram (CT) of the chest, should be done—even if the D-dimer test is not elevated.

Risk/Prevention

In 2004, the American College of Chest Physicians (ACCP) issued recommendations for travelers on long-distance flights lasting at least 6 hours. The ACCP came up with measures that are applicable to (1) all travelers and (2) those who are at increased risk.

Basic preventive measures for all travelers sitting for at least 6 hours:

Avoid constrictive clothing around the lower extremities and waist;

Drink plenty of fluids to maintain hydration;

Exercise and stretch the calf muscles*;

Take frequent walks up and down the aisle.

For travelers at increased risk. These are travelers with the following risk factors:

Previous DVT or phlebitis

Varicose veins

Obesity

Older age

Recent surgery, especially knee, hip, or abdominal surgery

Recent leg fracture

Pregnancy—especially during the third trimester and first month postpartum

Recent serious illness, such as cancer or congestive heart failure

High-estrogen contraceptives or hormone replacement therapy

Inherited or acquired blood clotting disorders

If you have one or more of the risk factors listed above, consult your doctor. There are two other options that can help to prevent DVT:

Support stockings (e.g., Jobst Gradient Hosiery) These compression stockings must be properly fitted so they won’t decrease circulation to your leg.

Anticoagulants (below): These drugs are reserved for people deemed at high risk.

An injection of low molecular weight heparin (Lovenox) or the newer anticoagulant, fondaparinux (Arixtra), can be administered shortly before departure. Fondaparinux is more effective than Lovenox, has a longer half-life, a more predictable response, and fewer side effects. Impractical to use.

Novel Oral Anticoagulants (NOAC) These drugs (Xarelto, Apixaban) can be taken by mouth, and unlike Coumadin, don’t require a blood test. Probably the best choice.

Low-dose warfarin (Coumadin) is highly effective, without significant adverse effects. A NOAC is probably a better choice for most people.

Aspirin is no longer recommended to prevent travel-related DVT.

Traveler’s Thrombosis in Perspective

In their report, Air Travel and Health, the British House of Lords Select Committee on Science and Technology commented:

“For healthy individuals, the risk of getting a clinically significant DVT solely because they are taking a flight seems to be exceedingly small. For those who are already at risk because they are subject to predisposing factors, there may be additional risk from flying, but it is not currently quantifiable. The current lack of sound information makes it difficult for individuals to make reasoned judgments about their personal DVT risk and, consequently, the precautions to take.” It is best, therefore to discuss the risk of travelers’ thrombosis with your physician and decide if you are a candidate for an anticoagulant drug.